class Bitmask
{
    private $bitmask;

    public function __construct($bitmask = 0)
    {
        $this->bitmask = $bitmask;
    }

    public function set($bit, $value)
    {
        if (!is_bool($value)) {
            throw \InvalidArgumentException('The value must be either true or false');
        }

        if ($value) {
            $this->setOn($bit);
        } else {
            $this->setOff($bit);
        }
    }

    public function toggle($bit)
    {
        $position = self::getPosition($bit);

        $this->bitmask ^= $position;
    }

    public function setOn($bit)
    {
        $position = self::getPosition($bit);

        $this->bitmask |= $position;
    }

    public function setOff($bit)
    {
        $position = self::getPosition($bit);

        $this->bitmask &= ~ $position;
    }

    public function get($bit)
    {
        $position = self::getPosition($bit);

        return $this->isOn($bit);
    }

    public function isOn($bit)
    {
        $position = self::getPosition($bit);

        return (bool) ($this->bitmask & $position);
    }

    public function isOff($bit)
    {
        $position = self::getPosition($bit);

        return ! (bool) ($this->bitmask & $position);
    }

    private static function getPosition($bit)
    {
        if (!is_integer($bit) || $bit < 1) {
            throw \InvalidArgumentException('The bit position must be a non-zero positive integer');
        }

        return pow(2, $bit);
    }
}